kilby94

I have a 91 Gt and have had a problem getting it to rev since the day i got it. It has 351w heads, E-303 cam, Typhoon upper and lower intake, msd coil and wires. When i first got the car it would not rev past 5,000 rpm in neutral or driving. I decided a couple of weeks ago to put a new set of valve springs in it because i was suspecting valve float. Well i ordered the Trick Flow kit and got them a couple of days ago. Put them in and there was a definate gain in power but it still was breaking up real bad around 5,400 rpm. Then i decided to replace the pick up coil in the dizzy, ended up getting a whole new distributor. Well that seemed to help a bit. This morning i got in my car while it was cold and it ran perfect, i hit 6,000 in first and second gear and the car was screaming. Then later on after it warmed up it was lacking power past 5,000. While in neutral slowly pushing in the throttle it will climb to 6,000 then when pegged to wot it starts sputtering and drops back down to 5,000. I guess next thing to do is replace fuel pump and regulator. Any ideas???

Oh yeah, there are no codes showing andit has new TFI.

mjr46

what size injectors are you running and hows the timing??? is the maf calibrated to the injectors??

kilby94

The fuel system is completely stock and so is the mass air sensor.

mjr46

so what's the history of the car?? did it ever run right or has it done this since you bought it or modded it yourself???

kilby94

I got the car through a trade and it was in pretty poor condition mechanically when i got it. It had alot of potential and was a clean car but whoever did the work on it was a complete idiot. It was hitting on 7 cylinders, showing like 15 codes, timing was 22*, basically it ran like crap. But it had an e-303 cam, rebuilt shortblock, 351w heads, and a few other small things. Slowly but surely i have been working out the kinks in this car as a side project while i'm in college. I replaced almost every sensor under the hood, rewired things, cleaned every electrical connection, set timing, then decided to buy parts. Well first of i got a new intake, and while i was putting it on i saw where whoever had put the stock lower intake back on the car the last time had covered up the number 2 intake port on the head with the gasket, which in turn was why the car was hitting on 7 cylinders. After intake and complete tune up i could feel that the car had very good power down low but wouldn't rev past 4,500 while under load, or 5,000 in neutral. And when it got that high in rpm it sounded like a mac truck. Next i decided to replace valve springs with the trick flow kit, that definately helped alot but then it wouldn't past 5,500 rpm. Next i replaced the dizzy thinking pick up coil was bad. That made it hit the rev limiter for the first time since i had bought the car(8 months). But it will only run good the first 10 minutes every day or while still cold. Once it warms up if you give it WOT in neutral it will stutter around 5,000, but if you ease into it it will hit the limiter over 6,000. I am thinking that i need an AFPR to jack up my fuel pressure. I have noticed that it drinks alot more fuel now that it runs better, and may be going lean in upper rpm.

92cobra

im gonna say its either o2 sensor related, maf related, and also do you know what voltage your tps has, i believe it should be right around 1 if i remeber right but dont quote me on that one. I would suggest cleaning your maf if you havent, and checking your o2 sensors and or replacing them, if you do you will get better gas milage if there old i can tell ya that from personal experience.

I had the same problem, however mine was the tfi module. But if the car works fine when cold and not warm, i would say the o2 sensors. Try changing those bro.

kilby94

Well i have put new bosch o2 sensors in already, tps is set to .098 volts, i have cleaned the MAF once but i might as well do it again. Thanks for input!